Blue Tort with bite marks

[GreenPufferfish]

Hi, I have a 55 gallon reef aquarium and within the last 2 days, have noticed my blue tort acro has a few bite marks on it. The coral itself is healthy and so are the rest of my corals. There are no corals close enough to sting the tort and it definitely looks as if small chunks have been bitten out of it. My 2 suspects of the crime are either my scopas tang (bite sizes match his mouth size) or maybe my sally light foot crab. The crab will some times climb on my corals and pick things off of them but I have never SEEN either the crab or tang damage coral. Does anyone have any experience with either of these creatures damaging coral? Any advice would help, Thanks!